Signaling system



n J. J. GILBERT 3,540

' SIGNALIN' SYSTEM Filed May 51, 1929 Fm. /v

Fla. 2

. I H .a/was ATTORNE? Patented June 2, 1931 UNITED STATES PATENT oFF cE"JOHN J. GILBERT, 0F DOUGLASTON, NEW YORK, ASSIGNOR TO BELL TELEPHONELABORATORIES, INCORPORATED, OF NEW YORK, N.Y., A CORPORATION" OF NEWYORK SIGNALING SYSTEM Application filed May 31, was. Serial no."367,489.

this conductor is grounded. These currents are of a very low frequency,ordinarily below one or two cycles per second.

It is evident that when the point in the earth,

at which the potential rise occurs which'is the cause of such currents,is comparatively close to the line terminal, the currents may becomequite heavy since the resistanceoto the nearest ground is comparativelylow.

' It has lately been found advantageous to use for the loading materialon long transmission lines, magnetic alloys which, atthe low magnetizingforces produced by the signaling currents, have a substantially constantpermeability and hardly measurable hysteresis losses. One such materialcomprises 'an alloy of iron, nickel and cobalt which, whenv properlyheat treated and in the proper proportions, has the desired propertiesreferred to above. It has been found that'the properties of such loadingmaterials may be seriously impaired when the material, is subjected tomagnetizing forces beyond the range within which those propertiesordinarily prevail. 1

An ob ect of the invention is to provide a slgnaling system using a longcontlnuously loaded signaling conductor and earth return in which theconductor is loaded with magnetic'material such as described above andin which the disturbing currents, such as earth currents, are reduced tosuch an extent that the loading material will not be deleteriouslyaffected by them.-

In accordance with the invention a network is provided at the terminalend of the signaling line, the impedance of which is such that signalingcurrents be passed without appreciable attenuation, whereas disturbingcurrents of lower frequencies than those of the signaling currents are"greatly attenuated. j I

'In the accompanying drawings .Fig. 1 is a simplified diagram of asignaling system arranged in accordance with the invention,

Fig. 2 is a graph showing the variations with the magnetizing force ofthe permeability of a loading material used in accordance with theinvention.

' Theinvention will now be described in connection with a submarinetelegraph sys-. tem such as shown in a simplified form in Fig. 1. Inthis figure 10 represents a terminalequipment whichmay be arranged I forelther transmission or reception of's1g-70 nals or for both. Theequipment '10 is connected through a network 11 to a submarine cable 12of considerable length, one end only of which is shown, and to a seaearth return 13. The sea earth return 13 may be a separate cable or maybe built intothe cable 12 for the desired distance. The cable 12comprises a central conductor 14' surrounded by a layer 15 of loadingmaterial, which maybe in the form'of a helical wrapping. of wire or tapeor in any-other desired form. The loading. material 15 may be an alloycomprising nickel, iron and cobalt 1n proportions and produced inaccordance with the disclosure ma copendmg patent applicationto G. W.'Elmen, Serial "No. 119,623, filed June 30, 1926 and "which has issued asPatent 1,715,647 on June' l,

1929, or as disclosed in acopending patent application to G. W. Elmen,Serial No;

220,387, filed September 19, 1927 and which I has ssued asPatent1,715,541 on June, 4, 1929, in accordance with which otheringredients, such as molybdenum and manganese, are ,added to the mainingredients.

In accordance with thesedisclosures 'certain of the alloys describedhave a constant permeability for magnetizing forces up-to about 4 gauss.The constancy of permeability in several other ofthe alloys disclosed isnot maintained beyond one or two gauss. When a cable of this type isconnected through a metallic circuit to ground at its terminal,disturbing currentswill flow in the conductor due to variations inpotential difference between the grounded conductor and the sea water atthe ocean xbottom. Such earth currents may assume considerablemagnitudes, especially when the point of 'potential rise --iscomparatively near a to the terminal-of the cable, in which-case thecomparatively weak signaling currents may be considered as beingsuperimposedupon the strong low frequency current. As has been describedin the copending application, Serial .No. 220,387, .referred .to. above,particularly in connection withj'Fig. i24 ofthat applicatiomsuch .acondition is detrimental to those properties. of the loading -materialwhich .aredesirable tion of the cable. The condition is illustratedsgraphicallysin Fig. 2 in which the abscissae :represent 'themagnetizing force exerted by. the superimposed signaling and 525 earthcurrents in the conductor, and the orqdinatesrepresent the correspondingpermeabilities oftheloading material. From this zgraph'it willl beobserved thatthepermeability remains constant for magnetizing.forcesupztoabout two gauss, and it has been-foundthatthis fixedpermeability will vprevail asrlongasthe magnetizing force is lvariedbelow. this limit. -However, when'the disturbing current increasesbeyond this 5 limit thegpermeabilityzisno longer constant but varies inaccordance with the-branch A of thegraph until the disturbing currenthasreached its maximum. T hen as this current :rec'edesthepermeabilityvaries in accordance 10 .withbranch B of the curve andattains-a greatly increased value when the magnetiz- Iing forcereachesbelow two .gauss, at the ,same timesasitl loses its constancybelow that :value. .It is evident-that the characteristics 5 of thecable are changed by-suchexcessive -magnetiz ati-on and thatthe; loss ofconstancy .of the permeability results in serious distor- :tion.of-thesignali'ng current,;which is particularly detrimental in the caser of tele- 1250 1911031 fl m nl a-tlon. .Several IIlQ vandhaving.Ka-low, impedanceforfrequencies have; been proposed whereby.the ,Vlfglll. con- .:dition' of the loading material may be re- 1:stored, but such :methods involve the use 7 either-of: automaticallyoperated equipment 255 or constant vigilance on the part of the.gstation attendant.

Inthe preferredemb'odiment shown in Fig. .1: therise ,of the earthcurrents to Values, at Y which the magnetizing force will exceed the.range within which the permeability re- ,mains constant, is-preventedby the inser- \tion. of the network 11. This network may -be-builtinvarious .ways but in accordance witlnthe system illustrated itcomprises a 6 transformer eoouplirrg .20 .betweenthe :ter-

for the efficient o pera- {of said magnetic property.

given a-sufiiciently high-value to reduce the intensity-of thesecurrents-in the desired de- 'ree.

It should be understood that a similar network may be introduced at theother terminal of the cable, which is not shown, to 30 protect-the otherend of the-cable in a similar manner and. for a similarpurpose.

A.formwh iclrthe network may assume is that of a high pass filtersuppressing all frequencies below a certain range and pass- .ingalllfrequ'encies abovetliat range with a practically negligibleattenuation, 'For telephony, where the lower frequencies below a fewhundred cycles are not utilized, the .filtermay suppress all frequenciesup to or almost upto the utilized range.

What is claimed is: a a V I 2,1.A continuously loaded signalingconductorhavinga magnetic loading with a desired magnetic propertywhich. is impaired bydisturbing current impulses iinsaid conductorexcessively strong as compared with signaling current impulses and anetwork associated with a terminal of said. cable for passing signalingcurrent impulsesand hav- 1100 f-lng a h gh lmpedance to.dlsturbingcurrent impulses of frequencies belowthose of the signalingcurrent impulses said impedance being high enoughto prevent the impair-.ment of said magnetic propertyby said dis-11 .torting impulses.

2.-A continuously loaded signaling con- .ductorm wh ch theloadingmaterial has a desired magnetic property 1 under the influence ofsignaling currents in the conductoniul said ,propertyz being impaired bydisturbing impulses of excessive strength, and .a networkconnectedtoatermmal of said cable comprising an mductance ,and .a capacitywithin. the range of; signaling impulses and 'rangexto reduce disturbingimpulses .sufliciently to prevent appreciable impairment f 1 3*20 A-continuouslyi loaded conductor in which the loading -material has asubstantially constant permeability within the range of intensities ofthe'signaling currents,

.the constancy of permeability within said 8125 range being impairedbydisturbing cur- ;rentsin excess of said rangeof intensities,

and a network connected to one ,terminalof said cable comprising atransformer winding stopping condenser and havii g low L impedance atfrequencies Within the signaling range and having a high impedance atfrequencies below that range to reduce ,disturbing impulses suiiicientlyfor the retention of the constancy of said permeability.

4. A continuously loaded cable havinga loading material of an alloymainly comprising nickel, iron and cobalt and heat treated to have aconstant permeability at the magnetizing forces exerted by the signalingcurrents in the conductor and the constancy of permeability of which isimpaired by excessive disturbing currents in the conductor, atransmitting circuit, and a network c011- nected between said circuitand one terminal of said cable, said network comprising a transformerwinding and a condenser in se ries with said winding and the impedanceof said network being such as to inappreciably attenuate the signalingcurrents and to substantially attenuate disturbing currents offrequencies below those of the signaling currents to substantiallyreduce their effect upon the constancy of said permeability.

In witness whereof, I hereunto subscribe my name this 15th day of May,1929.

JOHN J. GILBERT.

